This invention relates generally to semiconductor device technology and relates, more particularly, to semiconductor devices including a semiconductor-based substrate onto which is grown a crystalline oxide material.
Anisotropic crystals are known to possess properties or qualities which differ according to the direction of measurement. Particular examples are found in the anisotropy of critical phenomena like Curie ordering in magnetic and ferroelectric oxide structures. In some crystalline oxides, for example, the Curie ordering induces internal magnetic or electric fields at the onset of dipole ordering which is naturally disposed in a prescribed orientation relative to the body of the crystal. Furthermore, it is also known that the application of an externally-applied magnetic or electric field can re-orient (e.g. reverse) these induced internal magnetic or electric fields.
Heretofore, oxides have been incorporated within electronic devices, such as transistors, but only in the amorphous state or in a polycrystalline microstructure. Furthermore, these oxides (in the amorphous state or polycrystalline microstructure) do not exhibit any collective anisotropic behavior.
We have described in our co-pending application Ser. No. 08/692,343 filed Aug. 5, 1996 how alkaline earth and perovskite oxides can be grown unstrained and commensurately upon silicon to form a structure series of (AO).sub.n (A'BO.sub.3).sub.m, in which n and m are non-negative integer repeats of single plane commensurate oxide layers and that this structure can be utilized in the development of a new semiconductor technology. We have also described in our co-pending application Ser. No. 08/868,076 filed Jun. 3, 1997 that strain coupling to the anisotropy of crystal energy associated with ferroelectric phase transformations can be used to control gate-sized dependence of active metal-oxide-semiconductor (MOS) capacitors.
It is an object of the present invention to provide a new and improved structure for use in a semiconductor device including a semiconductor-based substrate upon which is grown a thin film of crystalline oxide wherein the crystalline oxide is capable of exhibiting anisotropic properties which are beneficial for operation of the devices.
Another object of the present invention is to provide such a structure wherein directional-dependent qualities of substantially all of the unit cells of the crystalline oxide are predisposed along a limited number of axes.
Still another object of the present invention is to provide such a structure wherein a directional-dependent quality of substantially all of the unit cells of the crystalline oxide are oriented in a plane parallel to the surface of the substrate.
Yet another object of the present invention is to provide such a structure wherein a directional-dependent quality of substantially all of the unit cells of the crystalline oxide is oriented along lines normal to the surface of the substrate.
A further object of the present invention is to provide a new and improved semiconductor device within which a crystalline oxide-on-silicon structure is incorporated and whose operation involves the application of an internally-applied or externally-applied field across the crystalline oxide thin film.